Keying device for electronic organs



June 3, 1952 R. H. CAMPBELL, JR., ET AL KEYING DEVICE FOR ELECTRONIC ORGANS Filed Dec. 8, 1950 3 Sheets-Sheet l ATTOR NEYE June 3, 1952 R. H. CAMPBELL, JR., ET AL 2,599,510

KEYING DEVICE FOR ELECTRONIC oRGANs Filed Dec. 8, 1950 5 Sheeis-Sheet 2 zocamflmwlf G www@ June 3, 1952 R. H. CAMPBELL, JR., ETAL 2,599,510

KEYINC DEVICE ECR ELECTRONIC oRCANs 5 Sheets-Sheet .'5

Filed Dec. 8 1950 v ATTORNEYS Patented June 3, 1952 UNITED STATES -TENT OFFICE KEYING DEVICE FOR ELECTRONHC ORGANS Application December 8, 1950, Serial No. 199,812

(Cl. Sib-1.01)

7 Claims. l

This invention relates to signal switching apparatus for useV in electrical musical instruments.

An object of this invention is to provide an improved signal switching device which may be manufactured efliciently and economically and which incorporates resistance circuit elements as part of the structure thereof.

Another object of this invention is to provide an improved signal switching device constructed so that it may be made with considerable saving of space and assembly labor.

Another object of this invention is to provide an inexpensive switching device incorporating associated circuit components in such a manner as to obviate wiring which would otherwise be necessary.

Another object of this invention is to provide a switching device having a physical arrangement such that considerable shunt capacitance is introduced between vcertain lparts thereof.

Still another object of this invention is to provide a switching device employing electrical im- 'pedance spacers having a high dielectric constant so as to provide electrical capacitance between the spaced parts.

Another object ofnthis invention is to provide a switching device for normally grounding the circuitlbetwee'n a source of oscillations and the load, this circuit consisting of a pair of spacers of resistance material contacting an intermediate leali` of the switching device that is grounded.

Other and further objects of this invention will be apparent to those skilled in the art to which it relates from the following speciiication, claims and drawing.

'Inaccordahce with this invention there is provided an electrical switching device adapted for use with electrical musical instruments wherein a number of sources of electrical oscillations of ...musical vfrequency are continuously operative.

This switching device may be actuated by manual cr pedal keys and is constructed with spacers of resistance material between one of the switch Contact leaves and the metal lugs connecting the switch to' the source of electrical oscillations and to the load circuit.

Further details of this invention are set forth in the following specification and drawing in which briey:

Figure 1 is a schematic wiring diagram of a circuit arrangement with which switching de 'vices of this invention may be employed;

Figure 2 is a side view of an embodiment of this switching device;

Figure 3 is a plan view of one of the metal inserts for the switch stack; and

Figure 4 is a view of a further embodiment of this invention showing a plurality of the switch devices connected together.

This invention relates more particularly to a signal switching device adapted for use in the switching circuit disclosed and claimed in copending application of Richard H. Campbell, Jr., SerialNo. 205,689, led January 12, 1951.

In the circuit diagram shown in Figure l, three sources Il), I I and I2 that supply electrical osciliations of musical frequencies are shown. The source I produces the musical frequency Cl 261.6 C. P. S.; the source II produces the frequency Cil 277.2 C. P. S.; and the source i2 produces the frequency C2 523.2 C. P. S., an octave above the frequency C1. It will be apparent that different numbers of such sources may be employed as will be necessary to cover the desired musical range. The output terminals I3, I4 and I5 of the sources IG, II and I2 are connected together to the ground It. The terminals I'I, I8 and I9 of the sources I0, Il and I2 respectively, are the high potential output terminals of these sources as opposed to the terminals I3, I4 and I5 which are grounded. The output terminal I'I of the source Il! is connected to one terminal of each of the high impedance resistors 20 and 2l. Likewise, the output terminal I8 of the source II is connected to a terminal of each of the high iinpedance resistors 22 and 23 and the terminal i9 of the source I2 is connected to a terminal of each of the high impedance resistors 24 and 25. The other terminals 26, 2'I, 28, 29, 3D and 3l of the resistors 20, 2|, 22, 23, 24 and 25, respectively, are connected to one side of the normally closed switches or keys 32, 33, 34, 35, 36 and 3l respectively. The other sides of all of these switches or keys are connected to the wire 44 which is grounded to the same ground as the wire I3.

The terminals 26, 2l, 23, 29, 30 and 3| are also connected to one side of each of the resistors 33, 3S, 4Q, 4I, t2 and 43 respectively. The other sides of the resistors 38, 40 and 42 are connected together to the output conductor 45 and the other side of the resistors 39, 4I and 43 are connected together to the output conductor 46. These output conductors 'i5 and 46 are connected to the output terminals il and 48. The other output terminals 49 and 5S of the output circuits are connected by the wire 5I to ground which in this case is the same ground as that to which the wires i5 and @4 are connected. Different numbers of output conductors such as conductors 45 and it may be employed and coupled to the sources through additional resistors such as resistors 25 and 3B. These additional resistors may also be connected to ground through a key such as the key 32.

In this arrangement the impedances 33, 39, 4B, 4|, 42 and 43 prevent the Various inputs to the common output circuits 45 and 46 from shunting each other excessively while the impedances 23, 2|, 22, 23, 24 and 25 prevent the output circuits connected to the sources I3, and I2 from overloading any of these sources.

It will be observed that the impedances 25 and 2| are connected across the output of the source I through the normally closed switches or keys 32 and 33 respectively. Likewise, the impedances 22 and 23 are connected across the source through the normally closed switches or keys 34 and 35 respectively, and the impedances 24 and 25 connected across the output of the source |2 through the normally closed switches or keys 35 and 31 respectively. These switches are thus normally at ground potential and prevent the transmission of signals to the output circuits 45 and 46 because these switches effectively ground the signal receiving terminals 25, 21, 28, 29, 33 and 3| of the resistors 38, 33, 43, 4|, 42 and 43, respectively.

When it is desired to transmit signals from the sources l5, and l2 to the output circuits 45 and 46 the appropriate keys of the group of keys 32, 33, 34, 35, 35 and 31 is opened to permit the desired signal to pass from the source to the output circuit. Thus, if it is desired to transmit a signal from the source I6 to the output circuit 46, the key 32 is opened removing the ground connection from the terminal 26 so that signal voltage may be applied to the circuit 46 from the source terminal |1 through the impedances 20 and 38 connected in series. In a similar manner signal voltage may be applied through the impedances 22 and 49 to the output conductor 46 simply by opening the key 34. In the case of the source |2 signal voltage therefrom may be applied to the output circuit 46 through the impedances 24 and 42 by opening the key 36. Signal voltages from the sources 0, Il and 2 may be applied to the output circuit 45 selectively by opening the keys 33, 35 and 31 respectively.

In this embodiment, the switches 32, 33, 34, 35, 35 and 31 are actuated by the playing keys of the musical instrument. Switches 32 and 31 are co-actuated by the C1 key of the instrument, so as to control respectively the fundamental or 8 pitch signal and the octave or 4' pitch signal of the C1 key. Likewise the switch 33 controls the 4 pitch signal of the C key, while another switch (not shown), co-actuated with the switch 33 by the C key, controls the 8 pitch signal of that key. The other switches of the instrument are actuated in like manner by the `various playing keys of the instrument.

In this circuit arrangement the electrostatic capacities of the switches 32, 33, 34, 35, 36 and 31 have no tendency to introduce signal leakage between the sources and the output or load circuits 45 and 46 since one side of the switch is connected to ground. Also, signals are transmitted between the sources and the load circuits when the switches are open so that signal leakage across the switch would be of no consequence. Furthermore, signal leakage in this apparatus can be virtually eliminated by arranging the component parts physically so as to minimize the capacitance between the points A and B.

In Figure '2, there is shown a physical embodiment of the switching device and coupling circuit constructed according to this invention. In this igure only one switching unit connecting a source, such as, the source Il] to an output circuit, is illustrated. However, it will be understood that as many switching units of the type shown in Figure 2 as is desired may be employed in the circuit arrangement shown in Figure 1. Further, it will be understood that two or more switching units of the type shown Figure 2 may be mounted, one above another, in a single stack as shown in Figure 4 and described hereinafter. In the latter case, each of the switches in one stack will be co-actuated by a single playmg'Iheysource lil has its terminal |1 connected to the metal insert 52 of the assembled stack 5.3 of the switching device. A plan view of this insert 52A is shown in Figure 3. An insulation spacer 54 is positioned on the top of'the metal insert 52 and a high resistance electrically conductive spacer 55 is positioned on the bottom of the insert 52. This resistance spacer 55. corresponds to the resistance unit 23 shown 1n Figure l.

On the top of the insulation spacer 54 is positioned the switch contact leaf 56 which is connected to ground and which supports an electrical contact 51 that corresponds to one of the contacts of the switch 32 shown in Figure 1. Ihe other contact 58 corresponding to the other contact of this switch 32 is supported by the switch contact leaf 59 that is positioned on the bottom of the conducting spacer 55. The connection between the leaf` 59 and the bottom of the resistance spacer 55 corresponds to the point 26 of the circuit shown in Figure 1.

Below the leaf 59 is positioned the spacer h65 which is also of electrically conducting material and the resistance of this spacer 53 corresponds to the resistance element 38 of Figure 1. The bottom of the spacer 60 is connected to the insert 6| which is connected to the output terminal 46a that corresponds to the terminal 43 of Figure l. Additional insulation spacers 62 and 63 are provided to the top and bottom, respectively, of the stack 53 and the stack may be held together by suitable machine screws 64 that are positioned in the holes formed in the stack. However, the inserts 52 and 6|, the leaves 56 and 59 and the resistance spacers 55 and 60 are insulated from these screws 64 by providing suitable spacing or sleeving therebetween.

Contacts 51 and 58 of the switch device are normally closed. However, the circuit of these contacts may be opened by applying a suitable actuating force to the end 65 of the leaf 55 so as to move this leaf upward. By providing a suitable leverage or linkage between several switches. such as the switch shown in Figure 2, a number of such switches may be opened at the same time.

Furthermore, the resistance spacers 55 and 63 may consist of a core of insulation material and the electrically conductive high resistance material may be painted or printed on the surface of these spacers, each of said painted or printed resistors being arranged to pass through a hole in the Spacer or around the edge thereof, and being insulated, except at its end points, by suitable lacquer or other material, so that the end points Only make contact with the surfaces of the inserts 52 and 6| and the leaf 59. In addition, the reSStVe Spacers 55 and 63 may be replaced by insulating Spacers of high dielectric constant if it is desired to use capacitive impedances for the impedances 29, 2i, 22, 23, 2t and 25 and 38, Si), 40, 14|,42 and 43 of Figure 1.

Where resistive rather than capacitive spacers are used, a certain amount of shunt capacitance will none the less be present due to the physical arrangement of the vresistive material between parallel conductors. Such capacitance is desirable since it will compensate for the tendency, otherwise present, wherein the capacitance between switch contacts, when open, shunts some of the higher frequency components of the signal and reduces the tonal brilliance.

It should be noted that the metal inserts, insulating spacers, and switch leaves and contacts shown in Figure 2 and described herein may be made of standard design and manufacture to reduce the cost thereof and facilitate assembly.

In Figure 4 there is shown a rear view of three switch stacks 6c, G1 and 58 similar to the stack of Figure 2 but containing two co-actuated switches in each stack, and forming a portion of a set of switch stacks as used in an electrical musical instrument. Certain points in these stacks are connected together by suitable shim material running through the stacks. The switches of stack 65 are actuated by the C1 key of the instrument, those of stack $1 by the Cil hey, and those of stack 68 by the C2 key. The stack 6% consists of the top insulation spacer 1E), a connecting shim 1I that runs through all of the stacks 85, G1 and 63 that is connected to grounded conductor Mib which corresponds to the ground connection i4 shown in Figure 1. Next to the shim 1I is the switch Contact leaf 12 corresponding to the leaf 56 of Figure 2 and Ibelow this is positioned the insulation spacer 13 which corresponds to the spacer t. Below the spacer 13 is the metal insert 14 that is connected to the terminal l1 of the source l. The high resistance electrically conductive spacer corresponding to the spacer of Figure 2, is positioned below the insert iii and the bottom of this resistance spacer rests on the Contact leaf 16 that corresponds to the leaf 59 of Figure 2'. High resistance spacer 'i1 corresponding to the spacer 60 of Figure 2 is positioned below the leaf 1t and above the insert 1t. The insert 18 is positioned in contact with the shim 19, which extends through all the stacks, constituting the first collector bus of the instrument, and which is connected to the output terminal 4S corresponding to the terminal 43 of Figure 1.

Below the connecting shim 19 in the stack 65 is an insulating spacer 10a and a second switching unit comprising a grounded connecting shim 11a in contact with the switch leaf 12a, the insulating spacer 13a, the metal insert 14a connected to the terminal I9 of the C2 523.2 C. P. S.

source l2, the high resistance spacer 15a, the

switch leaf 15a, the resistance spacer 11a, the metal insert 18a in contact with the connecting shim 19a. which constitutes the second collector bus of the instrument and which is connected to the output terminal 41 corresponding to the terminal 41 of Figure 1, and the bottom insulating spacer 1Gb. This second switch corresponds to the switch 31 of Figure 1.

The next stack 61 is similar to the stack 66 and consists of the top insulation spacer 30, the grounded shim' 1l contacting the leaf 82, the insulation spacer 83, the metal insert 84 connected to the source H, the high resistance spacer 85,

the switch leaf 86, the high resistance spacer 81,

the metal insert 88, the metal shim 19 which is connected to the output terminal 4B corresponding tothe terminal 48 of Figure 1, and the insulation. spacer a.

Below the shim 19 in the stack 61 is an insulating spacer 80a and a second switching unit comprising the grounded connecting shim 11a in contact with the switch leaf 82a, the insulating spacer 83a, the metal insert 84a connected to the C#2 oscillation source (not shown), the high resistance spacer 85a, the switch leaf 86a, the resistance spacer 81a, the metal insert 88a in contact with the connecting shim 19a and the insulation spacer 80h.

The stack 6,8 is similar to the stacks it and 61 and consists ofl the insulation spacer 9B, the grounded shim 1|, the switch leaf 92, the insulation spacer 93, the metal insert Q4 that is connected to the terminal I9 of the source i2, the high resistance spacer 95, the switch leaf 95, the high resistance spacer 91, the metal insert St, the metal shim 19 that is connected to the output terminal 48 and the insulation spacer 96a.

Belowv the shim 19 in the stack 68 is an insulating spacer a and a second switching unit comprising the grounded connecting shim 'Ha in contact with the switch leaf 92a, the insulating spacer 93a., the metal insert 94a connected to the oscillation source supplying the frequency C3 1046.4 C. P. S. (not shown), which is one octave abovethe frequency of the C2 source l2, the high resistance spacer 95a, the switch leaf ttc, the resistance spacer 91a, the metal insert Sila in contact with the connecting shim 19a and the insulation spacer 90b.

Of course, it will be observed that any number of these stacks may be positioned side by side as shown in Figure 4 and interconnected by suitable shims to complete the desired circuit between the stacks so as to make up the complete switch control of an electric organ. Furthermore, the high resistance spacers of the stacks 66, 61', and 68 may be replaced by suitable dielectric material if it is desired to replace these spacers with capacitive impedances.

By employing the shims for interconnecting the various stacks further simplicity in constructing the, unit is achieved and these shims may be produced by stamping corresponding metal parts for the several adjacent stacks from a single piece of sheet metal.

While we have described certain embodiments of this invention in detail, it is not desired to limit this invention to the exact details shown and described except in so far as they may be defined by the claims.

We claim:

1. A signal switching device for use in electrical musical instruments comprising a source of electrical oscillations of musical frequencies, a load circuit for converting the electrical oscillations from said source into musical sound vibrations, a keying device having a pair of conducting members, a pair of spacers of resistive material positioned between said members, a switch contact leaf between said pair of spacers of resistive material, a second switch contact leaf, normally closed contacts supported by said leaves, connections for connecting one of said members to said source of oscillations and the other of said members to said load circuit and connections for grounding said second switch contact leaf so that said rst mentioned switch contact leaf is grounded to prevent the transmission of electrical oscillations from said source to said load circuit until said normally closed contacts are opened.

2. A signal switching device for use in electrical musical instruments comprising a source of electrical oscillations of musical frequencies, said source having a high impedance output circuit, a load circuit for converting the electrical oscillations from said source into musical sound vibrations, a keying device having a pair of contact supporting leaves, means for grounding one of said leaves, a pair of members of resistive material positioned one on each side of the ungrounded one of said leaves, normally closed contacts supported by said leaves to prevent the transmission of electrical oscillations from said source to said load circuit, and means for opening said normally closed contacts to permit transmission of electrical oscillations to said load circuit.

3. A signal switching device for use in electrical musical instruments comprising a source of electrical oscillations of musical frequencies, a load circuit for converting the electrical oscillations from said source into musical sound vibrations, a`keying device having a switch contact leaf, a pair of conducting members of high resistance material, one of said members positioned on one side of said leaf and the other of said members positioned on the other side of said leaf, means for connecting one of said members to said source of oscillations, means for connecting the other of said members to said load circuit, normally closed contact means for grounding said switch contact leaf to prevent the transmission of electrical oscillations from said source to said load circuit until said normally closed contact means is opened.

4. A signal switching device for use in electrical musical instruments comprising a source of electrical oscillations of muscial frequencies, a load circuit for converting the electrical oscillations from said source into musical sound vibrations, a keying device having a switch contact leaf, a pair of impedence elements, one of said impedance elements positioned on one side of said leaf and the other of said impedance elements positioned on the other side of said leaf, means for connecting one of said impedance elements to said source of oscillations, means for connecting the other of said impedance elements to said load circuit, normally closed contact means for grounding said switch contact leaf to prevent the transmission of electrical oscillations from said source to said load circuit until said normally closed contact means is opened.

5. A signal switching device for use in electrical musical instruments comprising a source of electrical oscillations of musical frequencies, said source having a high impedance output circuit, a load circuit for converting the electrical oscillations from said source into musical sound vibrations, a keying device having a pair of contact supporting leaves, means for grounding one of said leaves, a pair of spacer members positioned one on each side of the ungrounded one of said leaves, a coating of high resistance electrically conducting material for said spacer members, normally closed contacts supported by said leaves to prevent the transmission of electrical oscillations from said source to said load circuit, and means for opening said normally closed contacts to permit transmission of elec trical oscillations to said load circuit.

6. A signal switching device for use in electrical musical instruments comprising a source of electrical oscillations of musical frequencies, a load circuit for converting the electrical oscillations from said source into musical sound vibrations, a keying device comprising a switch contact leaf, a second switch contact leaf, spacer means of resistive material for supporting at least one of said contact leaves, contacts supported by said leaves, and connections for connecting one terminal of said keying device to said source of oscillations and another terminal to said load circuit.

7. A signal switching device for use in electrical musical instruments comprising a source of electrical oscillations of musical frequencies, a load circuit for converting the electrical oscillations from said source into musical sound vibrations, a keying device having a pair of conducting members, spacers of resistive material positioned between said members, a switch contact leaf held against at least one of said spacers of resistive material, a second switch contact leaf, contacts supported by said leaves, and connections for connecting one of said members to said source of oscillations and the other of said members to said load circuit.

RICHARD H. CAMPBELL, JR. GEORGE H. HADDEN.

REFERENCES CTED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,543,990 De Forest June 30, 1925 2,250,065 Koehl July 22, 1941 2,492,320 Riggen Dec. 27, 1949 

